The present invention relates to a multi-stage centrifugal pump.
Single-stage or multi-stage centrifugal pumps are considered as belonging to the state of the art. In one aspect, the present invention relates to a multi-stage centrifugal pump whose drive shaft is arranged in a lying manner, i.e. arranged horizontally with normal operation. Such centrifugal pumps, as are considered as belonging to the state of the art, are, for example, offered by the company Grundfos in the series CH and CHN. These pumps have a pump housing with a shaft which is rotatably mounted therein and which, at its motor-side end, comprises at least one cylindrical section and connecting to this on the pump side, comprises a splined shaft section, on which impellers are arranged in a rotationally fixed manner. The impellers are clamped between an abutment ring seated on the shaft and the free shaft end. Such pumps are driven by an electric motor, whose drive shaft is connected in a rotationally fixed manner to the shaft mounted in the pump housing and carrying the impellers, and is connected to the pump via screw connections.
An axial face seal is provided, which is incorporated between the cylindrical shaft section and the pump housing, in order to permanently seal the stationary housing part of the pump with respect to the rotating shaft. This axial face seal comprises a stationary axial face seal ring which is sealed with respect to the pump housing, and a rotating axial face seal ring which is arranged on the shaft and is sealed with respect to the shaft. These rings comprise sliding axial sealing surfaces which are impinged to one another by a spring force. A spring, which is arranged between two spring holders and impinges the spring holders with a pressure force in opposite directions, is provided for mustering the spring force.
These known centrifugal pumps have proven their worth, in particular also the axial face seal described above. However, the arrangement described above necessitates a relatively large axial constructional length.
Against this background, it is one object of the present invention to design a centrifugal pump, such that its axial construction length may be reduced, with an otherwise equal hydraulic performance. Moreover, the design should be such that it may be manufactured as inexpensively as possible in large series manufacture. The present invention achieves these desirable features.